Torque control impact wrench

ABSTRACT

A ROTARY IMPACT WRENCH CONTAINING A MOTOR, A ROTARY IMPACT MECHANISM, AND A SPINDLE ADAPTED TO DRIVE A FASTENER. A RESILIENT TORSION BAR IS MOUNTED EITHER BETWEEN THE MOTOR AND THE IMPACT MECHANISM OR THE IMPACT MECHANISM AND THE SPINDLE AND INCLUDES A MEMBER FOR PRELOADING OR PREWINDING THE TORSION BAR SO THAT IT DOES NOT WIND UP FURTHER UNTIL AFTER THE TORQUE ON THE TORSIONS BAR EXCEEDS A SELECTED VALUE. A SHUT-OFF VALVE IN THE WRENCH IS CONNECTED TO A HOLLOW PASSAGE EXTENDING THROUGH THE TORSION BAR AND TERMINATING IN AN EXIT PORT WHICH IS NORMALLY CLOSED Y THE PRELOADING MEANS AND IS OPENED WHEN THE TORSION BAR WINDS UP FURTHER IN RESPONSE TO THE RISE OF TORQUE ON THE TORSION BAR ABOVE THE SELECTED VALUES OF TORQUE, RESULTING IN CREATING A FLUID SIGNAL WHICH CAUSES THE VALVE TO SHUT OFF THE POWER SUPPLY TO THE WRENCH MOTOR.

Sept. 28, 1971 HORNSCHUCH ETAL 3,608,131

TORQUE CONTROL IMPACT WRENCH Filed Oct. 2, 1969 2 Sheets-Sheet lINVENTORS HAN/V3 HOR/VSGHUCH REGINALD W PAULEY LEO KRAMER 7 ATTORNEYSept. 28, 1971 Filed 001;. 2, 1969 2 Sheets-Sheet 73 I}; a J {60 F/G. 3

H i: I P P 4 1: :o 40 43 7 a 7 35 INVENTORS 'ro,---,.-' 68 I HAN/VSHORNSCHUCH N w 6? REGINALD w PAULEY LE0 KRAMER 68 62 69/40 BY wrvmATTORNEY United States Patent 3,608,131 TORQUE CONTROL IMPACT WRENCHHanns Hornschuch, Easton, Pa., and Reginald W. Pauley,

Belle Mead, and Leo Kramer, Skillman, N.J., assignors to Ingersoll-RandCompany, New York, N.Y.

Filed Oct. 2, 1969, Ser. No. 863,152 Int. Cl. B25b 19/00 US. Cl. 173-1211 Claims ABSTRACT OF THE DISCLOSURE A rotary impact wrench containing amotor, a rotary impact mechanism, and a spindle adapted to drive afastener. A resilient torsion bar is mounted either between the motorand the impact mechanism or the impact mechanism and the spindle andincludes a member for preloading or prewinding the torsion bar so thatit does not wind up further until after the torque on the torsion barexceeds a selected value. A shut-off valve in the wrench is connected toa hollow passage extending through the torsion bar and terminating in anexit port which is normally closed by the preloading means and is openedwhen the torsion bar winds up further in response to the rise of torqueon the torsion bar above the selected value of torque, resulting increating a fluid signal which causes the valve to shut off the powersupply to the Wrench motor.

BACKGROUND OF INVENTION This invention relates to rotary impact wrencheshaving a torque-responsive means for stopping the wrench motor inresponse to a predetermined magnitude or value of torque applied by thewrench to a fastener, such as a nut or the like.

A conventional rotary impact wrench having an adjustable torque limitingmeans is disclosed in the US. Pat. No. 2,822,677 issued Feb. 11, 1958,to H. C. Reynolds. This tool includes an axially extending torsion barspring which is utilized to transmit rotary impacts to a fastener. Thetorsion bar is wound or prestressed to a predetermined value of torquecorresponding to the maximum torque load that is to be transmitted bythe torsion bar to the fastener. By being prestressed, the torsion bartransmits torque loads as a rigid non-deflecting coupling so long as thetransmitted torque is equal to or less than the prestressed torque onthe torsion bar. When the impact torque load applied to the torsion barby the rotary impact tool exceeds the prestressed torque of the torsionbar, the torsion bar begins acting as a spring, instead of a rigidcoupling, and deflects an additional amount and then rebounds to absorband dissipate the excessive impact torque load without transmitting itto the fastener. This torsion bar is commonly known as a prestressed orpreloaded torsion bar.

SUMMARY OF INVENTION A principal object of this invention is to providea novel torque-responsive motor shut-off system for an impact wrenchwhich is accurate and reliable.

Other important objects are: to provide a novel control system forsensing a torque load in an impact wrench and shutting off the wrenchmotor in response to a selected torque load; to provide a novel controlsystem for use with an impact wrench having a prestressed torsion barfor sensing a predetermined torque load and stopping the wrench inresponse to such predetermined torque load; and to provide a novelshut-off means for an impact wrench responsive to a predetermined torqueload on the impact wrench.

Patented Sept. 28, 1971 In general, the foregoing objects are attainedin an impact wrench containing a motor, a rotary impact mechanism, aspindle adapted to deliver a series of rotary impacts to a fastener, anda preloaded or prestressed torsion bar interconnecting either the motorto the impact mechanism or the impact mechanism to the spindle. Themotor is connected to its power supply through a fluid operated shut-offvalve which is connected to a passage extending through the torsion barand terminating in an exit port which is normally closed by theprestressing member of the torsion bar. When the torsion bar winds upfurther in response to the rise of torque on the torsion bar above aselected value of torque, the exit port is opened to create a fluidsignal which causes the shut-off valve to close thereby stopping theflow of power to the wrench motor.

BRIEF DESCRIPTION OF DRAWING The invention is disclosed in theaccompanying drawings wherein:

FIG. 1 is a fragmentary elevational view with parts cut away and shownin section of an impact wrench utilizing one embodiment of theinvention;

FIGS. 2, 3, and 4 are respective sections taken on lines 22 3-3, and 4-4in FIG. 1;

FIG. 5 is an enlarged fragmentary view with parts shown in section ofthe front spindle portion of the wrench in FIG. 1;

FIG. 6 is a fragmentary axial section of a second embodiment of theinvention; and

FIG. 7 is a section taken on the line 7-7 in FIG. 6.

DESCRIPTION OF PREFERRED EMBODIMENTS The first embodiment of the impacttool or wrench 1 shown in FIGS. 1 to 5 includes a casing 2 having afront nose 3, a pistol-shaped handle portion 4, and a rear cap 5. Thehandle 4 carries a trigger 6 which is connected to a throttle valve (notshown) and is operative to feed fluid pressure to the motor 7. The motor7 includes a hollow motor shaft 8 which is connected to a conventionalrotary impact mechanism 9 including a hammer 10 and an anvil 11. Theimpact mechanism 9 delivers rotary impacts to a spindle 12 in a mannerwhich is well known in the impact wrench art. All the foregoingstructure is conventional and, for that reason, is not described indetail.

The anvil .11 includes an integral forwardly extending tubular portion15 journaled in a bearing 16 mounted in the nose .3- of the impact toolcasing 2. The tubular portion 15 of the anvil surrounds an enlongatedtorsion spring or bar 17 having its rear end 18 formed as a square plugnon-rotatably anchored in a corresponding square hole in the anvil 11 sothat the impacts received by the anvil 11 from the hammer 10- arerigidly coupled to the upper end of the torsion bar .17. The forward endof the torsion bar 17 is integrally connected to the spindle 12 which isadapted to engage a socket (not shown) having a square hole fordetachably receiving the square forward drive end of the spindle 12.

The impact energy received by the anvil 11 is transmitted by the torsionbar 17 to a work piece. In order for the torsion bar 17 to accomplishthis, it must be wound or prestressed under a torque which is equal toor greater than the torque of the impacts being transmitted. Once thetorsion bar 17 is wound under a given torque load, it acts as a rigidcoupling in transmitting torque loads which are equal to or less thanthe prestressing torque of the torsion bar. In other words, so long asthe torque loads applied to the torsion bar 17 do not exceed itsprestressed torque, no further deflection of the torsion bar occurs.

When the impact load applied to the torsion bar 17 exceeds itsprestressing torque, the bar deflects or winds 3 up additionally undereach impact and then rebounds, resulting in the impact being absorbedsubstantially by the torsion bar without transmitting it to the workpiece. Thus the torsion bar 17 acts to limit the maximum torqueapplicable to a work piece to a value of torque equaling substantiallythe prestressed torque of the bar 17.

This invention relates to a system for detecting when the torsion barbegins winding up further and, in response thereto, shutting off theimpact wrench motor. The torsion bar 17 contains a hollow axial passage20 and a pair of radially extending wings 21 adjacent its front end 12.The axial passage 20 connects to a pair of branch ports 22 which extendradially outward and terminate in bleed ports 23 provided in the facesof the wings 21. Looking at FIG. 2, the branch passages 22 are arrangedin the form of a Z with the exit or bleed ports 23 being located in thefaces on the wings 21 facing in a clockwise direction, looking at FIG.2. A tube 25 containing a pair of diametrically located slots 26 in itsforward end is located on the torsion bar 17 with the slots 26 receivedover and keyed on the wings 21. The main portion of the tube 25 extendsrearwardly from the wings 21 and has a rear end 27 journaled in theforward end of the tubular portion of the anvil 11.

The exterior of the tubular portion 15 contains a series of helicallyarranged splines 29 and the exterior of the tube 25 contains a series oflongitudinally extending splines 30 which are also provided with athread 31. A sleeve 33 is mounted over both the tube 25 and the tubularportion 15 and includes cooperating axial flutes on its forward end andhelical flutes on its rear end to interconnect the tubular portion 15with the tube 25. A nut 34 is threaded on the thread 31 of the tube 25and engages the forward end of the sleeve 33 whereby it can be adjustedto wind up the torsion bar 17, thereby applying a preload torque to thebar 17. The sleeve 33 winds up the torsion bar 17 as it moves rearwardon the helical splines 29, due to the helix of the splines 29.

Due to the location of the bleed ports 23 on the faces of the wings 21facing in a clockwise direction, the sides of the slots 26 are urgedagainst the bleed ports 23 thereby sealing them, as the torsion bar isresiliently wound, by means of the nut 34 being turned on the tube 25 tomove the sleeve 33 rearwardly on the helical splines 29. The sidesurfaces of the slot 26 covering the bleed ports are machined to providea tight seal when engaged over the bleed ports 23, as shown in FIG. 2.Looking at FIG. 2, it can be seen that when the torque load on thetorsion bar 17 exceeds the prewound torque, the torsion bar will bewound up further in a counter-clockwise direction resulting in the bleedports 23 being opened by moving away from the side surfaces of the slot26 which normally seal the bleed ports 23. At this moment the venting ofthe ports 23 and the connecting fluid passage creates a signal which isutilized to shut off or stop the wrench motor 7.

The trigger 6 controls the feeding of fluid pressure to an inlet port 35opening into a chamber 36 containing a. shut-off valve means 37 which isnormally open and is operative, when closed, to shut off the flow ofpressure fluid to the tool motor 7. The chamber 36 is divided into aninlet space 38, a cylinder 39 and an outlet port 40 extending to themotor 7. The valve means 37 includes a valve seat 41 located between theinlet space 38 and the cylinder 39. As a result of this arrangement,pressure flows through the inlet port 35, the inlet 38, the valve seat41, the cylinder 39, and the outlet port 40 to the motor 7.

A spool valve 43 is slidably mounted in the cylinder 39. The valve 43includes a valve head portion 44 adapted to seat over the valve seat 41to close off the inlet space 38 from the cylinder 39. A spring 45 ismounted in the cylinder 39 to bias the valve 43 to a normally openposition, as shown in FIG. 1. The rear end of the cylinder 39 contains apilot port 46 connected to a passage 4 47 located in the rear cap 5. Theportion of the cylinder 39 containing the spring 45 and pilot port 46 istermed a pilot chamber 48.

The valve 43 contains a small leak passage 49 extending between theinlet space 38 and the pilot chamber 48. As a result of the leak passage49, fluid pressure applied to the inlet space 38 will slowly flow intothe pilot chamber 48 formed in the cylinder 39 at the lower end of thevalve 43. After fluid pressure is applied to the inlet space 38, thesudden exhausting of the pilot chamber 48 will result in the creation ofa differential fluid pressure acting across the valve 43 causing thevalve 43 to be quickly closed against the spring 45.

The passage 47 in the rear cap 5 connects to a tube 52 which extendsaxially from the rear cap 5 through the hollow motor shaft 8 and intothe rear end of the passage 20 in the torsion bar 17. Appropriate sealsare mounted at both ends of the tube 52 to prevent leaks from developingat these points.

As a result of the passage 20 in the torsion bar 17 being connected tothe pilot chamber 48 in the shut-off valve 37, the opening of the bleedports 23, in response to the rise of torque above the prewound torque onthe torsion bar, will exhaust the pilot chamber 48 and cause the spoolvalve 43 to shut off the air flow to the motor 7.

The nut 34 is provided at its rear face with a series of beveled gearteeth 53 adapted to engage the teeth 54 of a conventional Jacobs chuckkey 55 in the same manner that it is used on the conventional Iacobsdrill chuck. During the use of the chuck key 55 the axle pin 56 seats ina radially-opening hole provided in the sleeve 33 as shown in FIG. 5.

Means is provided for automatically locking the nut 34 in an adjustedposition on the sleeve 33 when the chuck key 55 is withdrawn from theoperative position shown in FIG. 5. The not 34- carries a tang '57slidably mounted therein in a corresponding longitudinally extendingslot and urged rearwardly by a spring 58. The forward edge of the sleeve33 is provided with a series of forwardly opening notches 59 adapted toreceive the tang 57 to lock the nut 34 against turning relative tothesleeve 33. A ring 51 surrounds the sleeve 33 and seats against the frontportion of the tang 57 where it can be moved forwardly to force the tang57 forward out of a notch 59. The ring 51 is wide enough to partiallycover the hole in the sleeve 33 when the chuck key 55 is removed so thatit must be moved forward to insert the axle pin 56 into its hole. Inmoving forward, the ring 51 forces the tang 57 out of the notch 59,thereby automatically unlocking the nut 34 so that it can be turned bythe chuck key 55 SECOND EMBODIMENT, FIGS. 6 and 7 The second embodiment60 of impact Wrench in FIGS. 6 and 7 differs from that of FIG. 1 byhaving the preloaded torsion bar located between the motor 7 and theimpact mechanism 9.

The hollow motor shaft 8 is provided with a rearward extension 61 andthe torsion bar 62 contains a central passage 63 connected by a shorthose 64 to a port 65 provided in the extension 61. The port 65 isconnected by a rotary joint to a passage 66 that runs to the pilotchamber 48 of the motor shut-off valve means 37.

The forward end of the torsion bar 62 carries a Z- shaped cross section67 locked between a slot provided in the front end of the motor shaft 8forming a pair of parallel surfaces 68. The Z-shaped cross section 67contains a cross passage 69 that is connected to the central passage 63and terminates in bleed ports 70 located at the end of each leg of theZ-shaped cross section, similar to the bleed ports 23' in the firstembodiment. The torsion bar 62 also includes an integral splineextension 71 located forward of the Z-shaped cross section 67 which isconnected in the usual manner to drive the impact mechanism 9.

Norm-ally the bleed ports 70 are sealed by being pressed against thesurfaces 68 of the motor shaft, due to the twist or prestress applied tothe torsion bar 62 in the same manner as in the first embodiment. Thiscondition will remain until the torque on the torsion bar 62 exceeds theprestressing torque load applied to the torsion bar. As soon as thebleed ports 70 are opened, they vent the air from the pilot chamber 48,causing the spool valve 43 to close and shut ed the supply air to themotor 7.

The rear end portion of the torsion bar 62 carries helical gear teeth 72engaging corresponding gear teeth on the shaft extension 61. The rearend face of the torsion bar 62 engages a screw 73 threaded into theextension 61, so that the forward movement of the screw 73 forces thetorsion bar 62 forward and twists it to increase the preload on thetorsion bar 62.

While several embodiments of the invention are shown and described indetail, this invention is not limited simply to the specificallydescribed embodiments, but contemplates other embodiments and variationswhich utilize the concepts and teachings of this invention.

We claim:

1. A rotary impact Wrench containing a system for measuring the torqueoutput of the wrench and for stopping the wrench motor in response to aselected value of torque, said Wrench comprising:

a driving train including a motor, a rotary impact mechanism, and aspindle adapted to deliver a series of rotary impacts to a fastener;

a resilient torsion member interconnected in said driving train totransmit a torque load in said train and adapted to yield in response tosaid torque load;

rigid means for winding and holding said resilient torsion member aselected amount to apply a predetermined preloaded value of torque to itpreventing it from yielding further until the torque load on the memberrises above said preloaded value of torque;

means for creating a signal in response to further yielding of saidresilient torsion member; and

means operative, in response to said signal, to stop said motor.

2. The wrench of claim -1 wherein:

said signal is a fluid signal.

3. The Wrench of claim 2 wherein:

said resilient torsion member is an axially extending torsion barcontaining an axially extending fluid passage having an exit port nearone end of said torsion bar; and

said rigid means seals said exit port until said predetermined value oftorque is reached whereupon said rigid means opens said exit port.

4. The wrench of claim 3 wherein:

said rigid means non-rotatably engages said one end of said torsion barand includes an engaging surface normally covering said exit port.

5. The wrench of claim 4 wherein:

said fluid passage in said torsion bar is connected to a valve operativeto shut off said motor in response to the opening of said exit port.

6. The Wrench of claim 5 wherein:

said torsion bar interconnects said rotary impact mechanism to saidspindle.

7. The wrench of claim 5 wherein:

said torsion bar interconnects said motor to said rotary impactmechanism.

8. The wrench of claim '5 wherein:

said rigid means includes a tubular portion surrounding said torsion barwhich is non-rotatably locked to the other end of said torsion bar andis connected to said one end of said torsion bar by a means adapted tohold said torsion bar in its preloaded wound condition.

9. A system for measuring the torque output of an impact wrenchincluding a motor, a rotary impact mechanism and a spindle adapted todeliver a series of rotary impacts to a fastener, the inventioncomprising:

a yieldable member interconnected between the motor and the impactmechanism and adapted to yield in response to the torque load on thespindle;

resilient means opposing the yielding of said yieldable member under atorque load;

means applying a preloa'd to said resilient means preventing saidyieldable member from yielding further until the torque load on saidspindle rises above a predetermined value; and

means creating a signal in response to further yielding of saidyieldable member thereby indicating that the torque load has risen abovesaid predetermined torque load.

10. The system of claim 9 including: means operative to stop the motorin response to said signal. 11. The system of claim 10 wherein: saidsignal is a fluid signal.

References Cited UNITED STATES PATENTS 2,808,916 10/1957 Johnson l73l22,822,677 2/1959 Reynolds 64-15 2,973,067 2/1961 Eddy 173l2 3,174,6063/1965 Hornschuch et al. 173-12 3,174,559 3/ 1965 Vaughn 173-l2 JAMES A.LEPPINK, Primary Examiner U.S. c1. X.R.

